GM LFX V6

Discussion in 'General Auto Conversion Discussion' started by pfarber, Apr 26, 2019.

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  1. Apr 26, 2019 #1

    pfarber

    pfarber

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    At this point in my build I'm looking at a motor. My E-AB can take up to an IO-540 so structurally by weight budget is 438lbs (O-540 dry weight).

    The LFX is 300hp, and GM lists the 'engine plant as shipped weight' of 345lbs. My guess this is with accessories like alternator/AC/emissions that could be removed.

    Since almost all the engine stuff I can find online seems to be for older motors or V8s I wanted to start a conversation about the possibility and pitfalls of using a new, all aluminum, V6 high performance motor.

    Heres some dyno info: https://gmpowertrain.com/2014_images/charts_lg/lfx_chart_equinox.jpg

    Two things come to mind. Fist, a standalone ECU/ECM. I have read that there are standalone ECUs that WOULD support VVT.

    Since this is a dual cam VVT motor would that be a reliability issue? My thoughts: NO. At a reasonable TBO you can rebuild before and long term issues crop up.

    Stand alone ECU: Lock out VVT? Keep it? I would assume that VVT plays a big part in the performance of the motor. Would/does locking out VVT make a 300hp motor an 150hp one? Or would you have to dyno it as see??

    Please keep posts on topic (yeah.. good luck with that lol).
     
  2. Apr 26, 2019 #2

    pictsidhe

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    VVT optimises the engine over a wide operating range. For an aircraft, it is not needed. Lock it out in the optimum position for full power, or remove it for some weight saving.
     
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  3. Apr 26, 2019 #3

    pfarber

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    If the ECU supports it wouldn't it be better to utilize it?

    I would derate the motor from 6800rpm/300hp to approx 5000rpm/250hp to get a sane reduction ratio (I don't know of any doing close to 2.5+:1).

    So to lock out the VVT you need to: (my guess)

    Dyno the engine and get the cam advance at 5000rpm
    Rig up a lockout / get a cam ground four times / worry about possible cam position sensors.

    That sounds expensive and deeper into the unknown.
     
  4. Apr 26, 2019 #4

    wsimpso1

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    Three major engine issues I can see. VVT, DI, and the factory ECU/sensor suite, none of which you should have in an airplane engine. VVT and DI enable the fat torque curve and great driveablity on the street. Turning a propellor you can only apply high torque in the upper quarter or so of the rpm range. In addition, DI has a couple poor habits. Best scheme for an airplane engine is to lock the VVT mechanisms at the high rpm high power setting. A careful examination is likely to show that a carefully selected hole and pin through the rotating mechanism will do and be VERY sturdy. There may even be racing hardware that holds the cams in one position. DI has a history of causing valve problems and is very difficult to optimize the fuel delivery for power and decent economy. Remove the DI injectors and plug the holes, then install conventional injectors of suitable size spraying fuel on the intake valve. After that, drive the fuel and ignition with a known very reliable ECU designed for the much smaller sensor suite needed in airplanes.

    The other issues are:

    Do they last when run at high power? My guess is they will do just fine, but we would need some data to know.

    Is there a suitable PSRU that will connect to the RFOB and connect to the flexplate? Does it have suitable vibration isolation for a V6 engine?

    Billski
     
  5. Apr 26, 2019 #5

    pfarber

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    You can strip out all factory ECU/PCM/BCM modules for aftermarket ECUs that do everything including VVT.

    My issue is that locking out VVT would make changes to the cam/drivetrain and without substantial testing could cause issues. At the least you need a few hours of dyno to find the sweet spot, then make 4 gears and or cams to lock the cams in place and still keep cap positioning sensors happy. So while it has not real use in an airplane, the motor is designed for it.. and undoing the millions of dollars and thousands of hours of GM testing would be foolish.

    I'm not even going to address the old wives tale of auto engines not being capable of prolonged high speed use. You can't be that out of touch with modern engine development to ask that.

    Is THIS SPECIFIC engine in use with a PSRU? No, not that I know of. I am not going to fear the TV monster like some people. The cost of analysis far exceeds cost of simply trying it on a stand for a few hours, then a tear down.
     
  6. Apr 27, 2019 #6

    Vigilant1

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    We'll, there you go! You know just what to do, things are just as you always thought they were, no need to gather more input. I'm guessing it works out this way often for you, which is a real time saver.
     
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  7. Apr 27, 2019 #7

    pictsidhe

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    Why are you asking our advice when you already know everything?
     
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  8. Apr 27, 2019 #8

    mm4440

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    Hi, realistic weights are difficult to get. I would take a good look at the LS-3 V-8. I bet the weight is close and it is more compact in some ways. 100 + hp more in a lower stressed engine with great after market support compared to the V-6.
    Murry
     
  9. Apr 27, 2019 #9

    rv6ejguy

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    As Bill said, DI and VVT will complicate things and are not needed on an aircraft application where the engine spends most of its life in a narrow range of load and rpm.
     
  10. Apr 27, 2019 #10

    wsimpso1

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    You ask for primary issues. I gave them. Take it or leave it but getting all snippy when someone is answering your questions is just telling us all to ignore you.

    I will proceed with a more detailed answer for the other folks who will find and read this thread.

    I KNOW the test regimen for engines at Ford and Chrysler, GM is similar, and as I said, this engine is probably OK. Some products fly through big durability tests first time, others need to be massaged and coaxed to only barely meet the criteria. Some less than really reliable products have escaped from the development mills. Maybe some folks are running boats or airboats with them. Maybe some Lemons racers or circle track guys are running them. Some data on how these engines do would be nice. This is part of the first adopter's risk...

    All the good wishes in the world won't make an existing PSRU bolt to the block and hook up to the crank. They do have to fit as sold or be adapted, all without putting axial load on the crank and with a vibe control system suitable to this power and number of cylinders. This too is part of the first adopter's risk...

    There is a history on the Honda V-6's and I believe with the AutoFlight PSRU, particularly in Titan T-51's. How that is typically done, and it seems successfully, is worth some looking in to, either to do the same power team or to expand it to the Chevy. This is how you reduce first adopter's risk...

    VVT, DI, and the factory ECU and suite of sensors - Please listen to Ross, he has done this WAY more than the rest of us put together.

    Billski
     
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  11. Apr 27, 2019 #11

    pfarber

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    So far the only issue is weather to delete VVT or keep it.

    To delete VVT the steps are:

    Determine optimum cam timing. (Requires a dyno. Not cheap)
    Machine parts to (at least 4 cam gears, possibly 4 new cams) to hold that timing. Test, run for reliability.
    Re-map ECU to (more dyno time), and a knowledgeable programmer/tuner.

    At the end of the day I've spent more than simply keep the VVT and its benefits since the stand alone ECU appears to support VVT on a dual cam engine.

    Do you have an easier way to delete VVT? If you do I'd like to hear it.

    Sadly v6 performance parts are just not readily available. And once you look at 2010 models and above the performance parts gets even thinner.
     
  12. Apr 27, 2019 #12

    pfarber

    pfarber

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    I have a different opinion so I must know it all? Wow.. you must be fun at parties.
     
  13. Apr 27, 2019 #13

    pfarber

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    Ok, so what are the benefits of locking out VVT? I can't remove the solenoids without plugging some galleys, so I might as well leave them in, and if the VVT parts are in there, why not use them is the ECU supports it?

    I understand VVT is not needed, but the pluses outweigh the minuses. Altering the factory heads and coming up with an pinning mechanism just screams 'point of failure'.

    Auto engines are not perfect airplane engines. I am willing to put factory reliability over a few lbs of weight or 'unneeded' accessories.

    I don't see an overriding reason to delete VVT other than 'not needed'. In order to maintain reliability, any talk of altering the factory components should have a big enough payoff to justify the risk and expense.
     
  14. Apr 27, 2019 #14

    pfarber

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    The LS-3 is to heavy. Yes, it makes HP, but my E-AB is happy at 200-250hp and the V6 does that at much less weight. My first option was an L33 (LS1 truck motor) but again, all up the weight was approaching 700lbs for HP that I could not use.

    The V6 is half the weight, makes the right amount of HP in the right RPM band.
     
  15. Apr 27, 2019 #15

    Hot Wings

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    If dyno time is too expensive maybe you should be looking for a flying plane or a FWF package that already exists!?
     
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  16. Apr 27, 2019 #16

    pfarber

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    VVT is not an issue. VVT is not causing issues on the LFX motor. No, it doesn't 'need' to be there, but considering the work needed to delete it vs simply use it... leaving it on has less risk.

    The only issue I can find with DI is dirty valves. Most manufactures have resolved this with an Firmware/ignition timing change. With the low TBO I would have as part of an experimental install (and every 100 hour scope the valves to track buildup) that is a much safer bet than plugging the DI ports and cobbling together an home brew TPI solution.

    Factory ECU.. I already said that a 3rd party, programmable, standalone ECU would be used. There would be no need for factory ECU and all the junk needed. Factory sensors would be retained, or if heavy duty replacements are available, used. Wiring would be up to aviation standards.

    I think what needs to be avoided is that making changes to the motor to make it 'less automotive' invites risk. Removing DI for a homebrew TPI system? No thanks. Removing VVT for no real reason (again, reliability) invites risk.

    As for the PSRU. There are several in the HP/RPM range. A bellhousing adapter is not uncommon and easily done.
     
  17. Apr 27, 2019 #17

    pfarber

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    Or follow a path that doesn't require it?

    There is no overriding reason to delete VVT. Its a car engine, VVT is built in, and taking it out has no real upside. The motor will be rebuilt at 500 or maybe 1000 hours. Rebuild is $800-1200. How many rebuilds (with complete VVT replacement) could I pay with dyno time to pin the cam for no real reason?
     
  18. Apr 27, 2019 #18

    pfarber

    pfarber

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    Regarding DI and valves:

    https://www.enginebuildermag.com/20...e-direct-injection-issues-facts-fictions-gdi/

    "“You’re not seeing this carbon buildup on race engines as much because they’re essentially wide open all the time,” Dickmeyer says. “The port velocity through the engine through the intake port and through the exhaust port is so fast that a lot of this stuff just doesn’t have the time to occur. It’s really the worst on a production vehicle where it sees a lot of throttle and idle time.”"

    So it seems that high RPM like on an airplane would mitigate a lot of the build up on the valves.
     
  19. Apr 27, 2019 #19

    Toobuilder

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    Not sure what the VVT phasing schedule looks like but some are pretty simple. Like "on or off". If you can get a technical report on the phasing then dyno time would not be needed.

    It's a good point to leave the system if its too hard to remove, but maybe it's really simple. Since nobody here seems to know, maybe table that discussion until you get eyes on it?
     
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  20. Apr 27, 2019 #20

    Hot Wings

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    Are there any that can do multiple injector events on each power stroke, or even provide the timing resolution required for single squirt DI?

    Moving on to a more productive thread...................
     
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